1. Field of the Invention
This invention relates in general to communications systems, and in particular generating wideband optical analog pulse positioned waveforms.
2. Description of Related Art
Communications satellites have become commonplace for use in many types of communications services, e.g., data transfer, voice communications, television spot beam coverage, and other data transfer applications. In addition to using radio frequency (RF) communications methods, optical methods are now being proposed to transfer data, because of the high data rates that optical communications links can support. Optical links have typically higher bandwidths than RF links, and can transmit data in both analog and digital formats.
Analog data transfer over optical links has been largely ignored in a digital encoding environment such as optical communications. However, many applications still require signal transfer in an analog format. Further, analog and digital optical communications links are typically degraded by noise floor factors, which is typically overcome by increasing transmitter power.
It can be seen, then, that there is a need in the art for a communications system that can transfer signals in an analog format. It can also be seen that there is a need in the art for optical communications links that can transfer signals in an analog format. It can also be seen that there is a need in the art for optical communications links that do not require increased transmitter power to overcome the limitations due to noise problems.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and system for generating single and multi-channel optical analog pulse-position modulation (A-PPM) waveforms. The system comprises a frequency modulator, a continuous wave optical source, and an optical modulator. The frequency modulator receives the analog signal and converts the analog signal into a frequency modulated signal. The optical modulator modulates the continuous wave optical source with the frequency modulated signal, to produce the optical pulse-position modulated signal.
The method comprises converting an analog input signal into a frequency modulated signal amplifying the frequency modulated signal and producing a large signal therein, modulating a continuous wave optical source with the large signal, therein producing the optical pulse-position modulation signal, and compressing the optical pulse-position modulation signal, therein increasing a processing gain.
The present invention provides a communications system that can transfer signals in an analog format. The present invention also provides optical communications links that can transfer signals in an analog format. The present invention also provides optical communications links that do not require increased transmitter power to overcome the limitations due to noise problems.